Field cooling memory effect in Bi2212 and Bi2223 single crystals

A memory effect in the Josephson vortex system created by a magnetic field in the highly anisotropic superconductors Bi2212 and Bi2223 is demonstrated using microwave power absorption. This surprising effect appears despite a very low viscosity of Josephson vortices compared to Abrikosov vortices. The superconductor is field-cooled in a DC magnetic field H_m oriented parallel to the CuO planes through the critical temperature T_c down to 4K, with subsequent reduction of the field to zero and again above H _m. A large microwave power absorption signal is observed at a magnetic field just above the cooling field, clearly indicating a memory effect. The dependence of the signal on a deviation of the magnetic field from H _m is the same for a wide range of H_m from 1500 to 17 000G.